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In article ,
"Richard Fry" wrote: "Telamon" wrote Yes that is true that the fundamental by itself will not produce harmonics of lower frequency but the fundamental is being modulated by data so mixed products of variable data transmitted mixing with the carrier will produce frequency energy above and below the fundamental. If you have long strings of ones or zeros the mixed frequencies will be as low as the inverse of the period of low frequency data rates. ____________ The spectrum occupied by a data pulse is dependent on the rise and fall times of the pulse, not on the pulse duration. If the rise and fall times are constant, spectral bandwidth also will be constant. Only the distribution of energy within that spectrum will vary for pulses of different lengths (half-amplitude durations). Snip Yes and that would be the case for NRZ data or non return to zero data. -- Telamon Ventura, California |
#2
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"Telamon" wrote
Yes and that would be the case for NRZ data or non return to zero data. ___________ Once past the pulse transition, NRZ "data" is nothing but a different value of DC -- the bandwidth of which is infinitely small. If NRZ data is amplitude modulated onto a carrier via a DC-coupled modulator, then the effect is to change the amplitude of the carrier from one steady-state value to another. The occupied spectrum is infinitely small for steady-state carriers. For frequency modulation, DC-coupled NRZ data will change the carrier from one frequency to another, each of which will be infinitely small during steady-state conditions. RF |
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